[dejaentendu0]

As already mentioned, you need to take a test to find out for certain. I'd advise you take one as soon as possible, so that if you are, you can set up the necessary appointments and start prenatal.
I DO want to mention though, that if you keep thinking your pregnant, your mind has a habit of showing the symptoms. I haven't had my period in a little over thirty days and I kept worrying that I was - so much so that my stomach became bigger and sore, my breasts were tender, and I felt nauseous. However, I just recently took two tests. And once assured that I wasn't, they slowly faded back to normal.
Your mind can do weird things to your body if you're convinced of something.

May I advise you, if you aren't pregnant, to talk to a doctor/OBGYN about getting some form of birth control or investing in a package of condoms - just in case?
Also, your ex sounds pretty crappy for leaving you in this situation and denying he could be a father. Find a better man next time. Any man that'll leave you when you need him most, isn't worth your time.